A study of antibody mediated cornea allograft protection will be undertaken in an effort to determine if the protective effect is due to masking of graft antigens or to an inhibitory effect on immunocompetent cells. The binding and persistence of guinea pig anti-rabbit lymphocyte globulin (ALG) and succinylated antilymphocyte globulin (S-ALG) on rabbit corneal allografts will be measured. Lymphocytes from rats and mice immunized with allogeneic cells or from nonimmune animals will be incubated in alloantibody directed against their alloantigens and then transferred to the anterior eye chamber of allogeneic recipients. In similar experiments untreated lymphocytes and alloantibody specific for the recipient's alloantigens will be injected into the anterior chamber. The degree of endothelial damage in each case will be compared to that observed when no antibody is present and should indicate how inhibition of immune recognition of corneal cell antigens by lymphocytes is blocked by antibody. The ability of lymphocytes to respond to corneal cells in vitro with and without the presence of alloantibody will be assayed by trititated thymidine incorporation of the former and by Chromium 51 release from the latter. Studies of the cytotoxic potential of homologous anti-HL-A antibody on human cornea cells in vitro has demonstrated the susceptibility of these cells. Further experiments will entail chemical modification of anti-HL-A antibody to inhibit its capacity to fix complement but not its antigen binding capacity. The modified antibody will be tested for its ability to protect human cornea cells from immune attack in vitro. This approach should indicate, as will the other studies, the mechanism of the protection afforded by antibody and suggest if it would be useful in clinical trials.